In general, in combustion furnaces typified by industrial furnaces such as a steel furnace, a heating furnace and a deodorizing furnace, a combustion control is performed by a combustion controlling system while monitoring a combustion state of a burner disposed in the combustion furnace, a furnace temperature, a pressure of a combustion air, and a pressure of a fuel to be supplied to the burner, to thereby ensure the safety of combustion.
For example, in the combustion controlling system, in a state in which the combustion of the burner is abnormal and a flame has disappeared or a state close to that state (hereinafter referred to as “flame failure”), a control is performed so that a safety shutoff valve is closed within a flame extinction safety time to stop the supply of a fuel to the burner based on a safety standard related to industrial combustion furnaces (EN 298: 2012, EN 746-2: 2010). In that case, the flame extinction safety time is a time to start with a signal indicating that the flame has disappeared and to end with a signal indicating that the safety shutoff valve of the gas fuel supply is closed (refer to JIS B 8407).
As the combustion controlling system, for example, as disclosed in Japanese Unexamined Patent Application Publication No. H11-218034, there is a multi-burner system that controls combustion of a plurality of burners installed in a common combustion chamber. In the present specification, the combustion chamber means a space in which combustion is controlled under a condition (parameter) where a temperature, a pressure or the like is the same, and is also called “zone” below.
In general, the multi-burner system employs a star type device configuration including a burner controller provided corresponding to each burner and a safety controlling device for controlling each burner controller. For that reason, a communication between the respective burner controllers is not performed directly but indirectly through a safety controlling device on an upstream side.